IGCSE Physics: Thermal Physics

Thermal physics is where IGCSE Physics meets everyday life. Examiners want you to link microscopic behaviour (particle motion) to macroscopic observations (temperature, pressure, change of state). The long-answer questions in Paper 4 almost always hinge on a careful particle-model explanation.

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What you need to master

1Kinetic particle model: states of matter, Brownian motion and evidence for particles.
2Temperature scales, thermometers and thermal equilibrium.
3Specific heat capacity: definition, experiment and calculations.
4Latent heat of fusion and vaporisation; interpreting heating/cooling graphs.
5Gas laws: relationship between pressure, volume and temperature.
6Heat transfer: conduction, convection, radiation and practical applications.

Key formulas

E = mcΔθ

E = mL

pV = constant (at constant T)

p/T = constant (at constant V)

V/T = constant (at constant p)

Examiner tips

•For kinetic-model questions, always refer to particles "moving faster" and "colliding more" — vague words like "hotter" lose marks.
•State the quantity that is kept constant when using gas laws.
•Always include units on specific heat (J/(kg·°C)) and latent heat (J/kg).

Common mistakes to avoid

•Saying particles "get bigger" when heated — they do not; the gaps between them increase.
•Confusing heat (energy in joules) with temperature (°C or K).
•Forgetting to convert °C to K before applying gas laws that need absolute temperature.